This issue occurs due to the limitation in the Veritas Update feature.
Perform 1 or 2.
1. In case of Veritas Update, users with VSR 18 /18 SP1/18 SP2/18 SP3 must update to VSR 18 SP4, After updating to VSR 18 SP4, users can run Veritas Update to get VSR 18 SP5 that is listed as an update available.
2. In case of Download Center, users with VSR 18 /18 SP1/18 SP2/18 SP3 should download the VSR 18 SP5 Patch from the Download Center and update to VSR 18 SP5 by manually installing the VSR 18 SP5 patch.